Integrate rubygems.org and gittip

Setting up a pull request early and pushing early and often so as to get feedback on any desired changes early.  Will update when I actually want this merged.

Also, it's important to note that this is only gem level integration.  Maintainer specific integration comes next.

Current status:

- Enough functionality to look like it works.
- Need an icon for enabling gittip if we keep the current UI.
- Need to do callbacks over to gittip on update so that this all actually works.